Society 18/04/2021

This is how the AstraZeneca vaccine works

Targeted for links to rare cases of thrombosis, it uses chimpanzee adenovirus as its platform

2 min
One vial of AstraZeneka vaccine

BarcelonaMarred by constant distribution breaches, changes in age criteria and now also dogged by its link to rare cases of thrombosis, the Oxford/AstraZeneca (UK) vaccine was approved for use on 29 January 2021 and the UK had already licensed it in December. The technology it uses - genetically modified attenuated virus, in this case chimpanzee adenovirus - has previously been used to produce vaccines against Ebola and Zika. It is the same mechanism of action as the Janssen and Russian Sputnik V vaccines. It is licensed in a dozen countries, although some have stopped vaccination after the cases of thrombosis.

1.
How does it work?
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  • A genetically modified, attenuated virus, the non-replicating chimpanzee adenovirus, is introduced into the body as a platform that carries the S protein.
  • The virus contains the genetic information for our cells to manufacture covid-19 virus proteins, such as the S protein.
  • Our body recognizes this protein as foreign and produces antibodies and T-lymphocytes.
  • If we become infected, the antibodies will block the virus and the lymphocytes will destroy the infected cells.
  • The vaccine cannot cause disease from adenovirus or SARS-CoV-2.
2.
To whom is it administered?
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  • Indicated for: People aged between 18 and 69.
  • In Catalonia it is now administered to: People between 60 and 69 years old. Before the European Medicines Agency (EME) linked it to rare cases of thrombosis, the so-called essential groups (teachers, police, firefighters, and so on) up to 55 years of age had been vaccinated.
  • It is contraindicated for: People with severe hypersensitivity to any previous dose or any of the components.
  • Pregnancy: As there are not enough studies in pregnancy, it is also not recommended for pregnant women, although there are no indications of safety concerns. For pregnant women who are in a group where vaccination is recommended, e.g. healthcare workers, vaccination can be considered according to the benefit/risk assessment.
  • Vaccination should be postponed in case of: Having a severe acute illness, but not in case of having a mild illness without fever.
  • It is not recommended in: In patients with severe immunosuppression, uncontrolled cardiovascular, hepatic, renal, renal, metabolic, endocrine and severe neurological diseases there are no consistent data available and the use of other vaccines is recommended.
  • If the age limit is not lifted, it is also not recommended for people over 70 years of age.
3.
Conservation and administration
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  • Storage: It is stored at a temperature between 2 and 8 degrees, has a life of up to six months and should not be frozen or diluted.
  • Administration schedule: Two doses are administered with an interval of between 10 and 12 weeks (between 70 and 84 days).
  • Efficacy: It offers 81.3% protection against covid after the second dose.
  • Cost: The approximate cost per dose is of 2 euros.
4.
Adverse effects
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  • The most frequent are: Pain at the injection site, fatigue or tiredness, headache, chills, nausea, joint pain and fever.
  • Intensity: Most are mild or moderate in intensity and disappear after a few days.
  • Side effects: The European Medicines Agency (EME) has concluded that thrombi may be a side effect of the AstraZeneca vaccine in "very rare" cases but recommends continuing vaccination, arguing that the benefits outweigh the risks.
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